This invention relates to a battery powered timing control circuit that drives a stepper motor, and includes a temperature-responsive battery heater.
As is well known in the art fields of battery powered apparatus and auxiliary battery powered apparatus, whenever a battery supplies a DC voltage in extremely cold temperatures, the temperature may substantially reduce the performance of the battery. This probelm acutely affects timing control apparatus subject to extremely cold external environments that rely on a stepper motor to turn the dial of a timing mechanism. In timing control circuits that drive a stepper motor, maintaining a substantially constant temperature in the vicinity of the battery allows for recharging of the battery without causing damage to the battery that might result if recharged at extremely cold temperatures. Also, in a timing control circuit with a full-wave recitified and recharging circuit that continually recharges the battery, a temporary AC power failure will stop the recharging of the battery, and require that the battery supply a substantially constant voltage to both the timing control circuit and the stepper motor until the AC power is restored.
The prior art evidences no battery powered time control circuits in combination with a temperature-responsive heating element designed to carefully monitor the temperature of the battery supply to produce a substantially constant voltage to the timing control circuit and the stepper motor, irrespective of ambient temperature change in the vicinity of the battery.